First of all, I am very much a newbie so please bear with me. And talk very slowly. I have a 515E router with NAT setup. Internal IPs look like 172.16.10.x and external IPs look like 208.119.81.x. Our DNS is setup inside the network (so I can't setup an alias - right?). I have one application running on an internal server that needs to be accessed by both outside and inside the network. This application needs to be accessed via the external IP address. Everything works great outside the network but, of course, the application cannot be accessed from within the network via the external IP. I've tried searching for some type of resolution to this problem and keep coming across setting up a loopback. Is it even possible to setup a loopback on a 515E? If so, how do I go about doing that? Would setting up a loopback solve my problem? Any other suggestions on how to accomplish this? Thanks!
you mean PIX 515E i guess. it's a firewall not a router, therefore you can't create loopback interface.
Depending on which version of PIX you are currently running, if it's version 7.x or higher, then you can configure the following:
same-security-traffic permit intra-interface
static (inside,inside) 208.119.81.x 172.16.10.x netmask 255.255.255.255
Then assuming that you have "nat (inside) 1 0 0", then configure the following:
global (inside) 1 interface
Hope that helps.